Update (3:15 pm ET): i24News is reporting that Israel has called up some reserve units for air defense, home front and intelligence as Defense Minister Avigdor Liberman consults with military leaders at IDF headquarters in Tel Aviv.

i24 reported that the call-up orders for Israel air defense and its home front and intelligence forces came about an hour after the suspicious activity - which has not been identified - was detected.

"Following the identification of irregular activity of Iranian forces in Syria, the IDF has decided to change the civilian protection instructions in the Golan Heights and instructs local authorities to unlock and ready shelters in the area," a statement from the army said.

"The Israeli public should remain attentive to IDF instructions that will be given if necessary."

"Additionally, defense systems have been deployed and IDF troops are on high alert for an attack.

The IDF is prepared for various scenarios and warns that any aggression against Israel will be met with a severe response."

The US embassy in Tel Aviv also issued a warning to government employees to avoid the Heights.

"Due to the recent tensions in the region, until further notice, U.S. government employees are required to obtain advance approval if they wish to travel to the Golan Heights," the statement posted on Tuesday afternoon local time said.

Some senior Iranian officials vowed to take revenge on Israel for the Hama attack. However, Iranian President Hassan Rouhani said Tuesday that the country would remain in the hopes of forging a workaround with the five other parties to the agreement.

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The Israeli Defense Force says it has identified "unusual movements of Iranian forces in Syria" and has responded by ordering the opening of shelters along the Golan Heights - its border area with Syria - and ordering its troops to be on "heightened alert" for an attack.

According to Reuters, Israel has instructed local authorities in the border region to "unlock and ready [bomb] shelters".

#BREAKING: Israeli IDF says it has identified "unusual movements of Iranian forces in Syria", ordered the opening of Shelters in the Golan Heights and are saying: "We are on hightend alert, and forces are deployed & we are ready for all scenarios" (Video: @IDFSpokesperson) pic.twitter.com/zxwL222dRX

The Israeli Air Force, which has conducted many of Israel's attacks against Iranian forces in Syria, warned that "any aggression against Israel will be met with a severe response."

The IDF has detected irregular Iranian activity in Syria and is preparing the civilian population on the Golan Heights accordingly, as well as defensive systems. Any aggression against Israel will be met with a severe response.

The news arrived just minutes before President Donald Trump announced his decision to pull the US out of the Joint Comprehensive Plan of Action - otherwise known as the Iran deal. During the announcement, he referenced a presentation given by Israeli President Benjamin Netanyahu outlining Iran's efforts to secretly build up a nuclear arms program. Critics of the presentation said that Netanyahu didn't tell the international community anything new.

Shortly after Trump spoke, Netanyahu said the deal gave Iran billions of dollars to fund its efforts to spread terror across the region. Iran has long been criticized for its partnership with Lebanon's Hezbollah and for funding militias in Syria and Iraq, as well as the Houthi rebels fighting the Saudi Arabia-backed establishment in Yemen.

Since the beginning of the Syrian Civil War seven years ago, Israeli forces have launched more than 100 attacks on Iranian forces working with the Syrian regime to fight off rebels and ISIS.

Last month, a senior Israeli military official admitted to the New York Times that an Israeli drone had killed 14 people, half of whom were Iranian, during an attack on Syria's T4 air base, which is located about halfway between Palmyra and Homs.

Defense stocks are rallying as investors assume - correctly - that the risk of an all-out military conflict between longtime enemies Israel and Iran - a conflict that could push the world into World War III - has never been higher.

On Sunday, Israeli media reported that military and intelligence forces had discovered that Iranian forces, including Hezbollah and local Shiite militias, were preparing for some kind of attack on Israel, per RT.